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Motorsport Wheel Alignment: Setting Up Adjustable Suspension Arms

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Setting Up Adjustable Suspension Arms


00:00 - When it comes to fitting aftermarket suspension arms into our cars, one of the first jobs we need to do is make sure that we have these arms correctly adjusted before we install them.
00:10 Now when we're doing this, there are a variety of ways we can go about this.
00:13 One of the easiest ways of course is to start by replicating at least closely the geometry or measurements of the factory arm.
00:21 This at least means that once we get the arms into location, we're going to know that our alignment is going to at least be in the ballpark and we can start making our adjustments from here.
00:32 Of course we're not going to need to be pinpoint accurate here because the whole purpose of fitting aftermarket suspension arms is to allow us to make changes that we can't with the factory arms in place.
00:44 With this in mind, we're going to go through a couple of demonstrations here, we're going to have a look at how we can measure our stock lower control arm for our Toyota 86 and replicate those measurements on our aftermarket fabricated lower control arms.
00:58 We'll also have a look at a pair of toe control arms and see how we can adjust these to make sure that they are equal.
01:04 Now the process we're going to go through will depend on exactly what we're trying to achieve.
01:09 I've just mentioned that we're not going to be trying to get pinpoint accurate here because we will be making changes beyond what's possible with the factory lower control arm.
01:18 However if you are in a situation where you do actually want to accurately replicate the factory measurements then the best way of doing this is to start by making a jig using the factory lower control arm to make that jig and then putting your aftermarket control arms into that jig and adjusting them until everything fits.
01:35 This way we can be 100% certain that the measurements on our aftermarket arms will match the factory.
01:42 Now that's quite an involved process, it requires some fabrication and frankly is probably beyond the scope of this course.
01:49 And again, we're fitting these components so that we can make adjustments that aren't possible with the factory arms.
01:55 So let's get stuck in, what we're going to do is make some measurements on this arm.
01:59 First of all what we need to do is just have a look at the arm and see what we're dealing with here and in particular, you can see that this factory arm is already fitted with a set of Whiteline aftermarket suspension bushes.
02:09 In particular this suspension bush here, the front suspension bush, also has made some caster adjustment.
02:15 We can see that it is an eccentric bush and this has offset the arm towards the inside of the chassis and what this does is it has the effect of pulling the lower ball joint forward and of course that adds positive caster to our wheel.
02:28 Now that's not a bad thing and we will be replicating this as closely as possible to start with.
02:34 So let's take our measurements, again we're not going to be pinpoint accurate here.
02:38 We're just trying to get an approximation and as long as we're within a millimetre of so, we're going to be close enough for our purposes.
02:45 Now in order to make our measurements I'm just going to be using a 600 millimetre stainless steel ruler.
02:51 And what we're going to do is just try and find as close as we can, the centre of our caster bush and we're going to run our ruler to the centre of our rear inner bush.
03:01 And at the moment we can see that the measurement on that ruler is around about 352 millimetres.
03:07 What we can now do is document this measurement so that we're going to be able to replicate this without forgetting it.
03:13 But also so that we've got some documentation of the factory components later on in our file for this particular vehicle.
03:19 Let's move on and we'll take some more measurements.
03:22 When it comes to making measurements between our suspension bushes and our lower ball joint, I find it's actually easier to get an accurate measurement if we turn the arm over and what we're going to be doing is measuring to the centre of the lower ball joint at this point here.
03:35 If we measure this at the top, it's very difficult to be accurate because we can influence our measurements quite a lot depending on the actual location or angulation of the ball joint when we take our measurements.
03:45 So let's go ahead and take our next two measurements.
04:00 So at this point we've got our approximate measurements taken off our factory lower control arm, what we want to do now is apply these or transfer these across to our aftermarket lower control arms.
04:10 So we've got everything documented there and again we're going to be able to save this in our record for that car for future reference.
04:16 Let's get one of our lower control arms out now and we'll have a look at how we can make these adjustments.
04:21 So we've got our aftermarket lower control arm here and before we apply any changes to this, it's always a good idea to just have a look at the available adjustments and see what the adjustments will actually achieve.
04:33 In this case we can see that at each point, the factory rubber bushes or the aftermarket urethane bushes have been replaced with spherical bearings and this is going to remove any of that potential compliance from those factory bushes.
04:45 Now the way I've got this arm laid out, this is the right lower control arm and the front of the car would be facing this way.
04:52 So this particular spherical bearing here faces the front of the car and of course this is our inner rear bushing.
04:59 We've got a spherical bearing replacing our ball joint or our lower ball joint and this will be mated to a stud that goes through the factory hub.
05:08 Now the adjustments we've got here is we can obviously extend or reduce the length of these two rod ends.
05:15 And we need to understand what those will affect.
05:18 So for example, if we extend this particular rod end here, it's going to achieve two things.
05:23 First of all it's going to extend our track width because it will move our lower ball joint further out from the centreline of the car.
05:30 However this ball joint will also move in an arc.
05:34 So as it moves out it will also move forward, so this is actually going to achieve two aims, it's going to increase our track but it will also increase positive caster.
05:43 Likewise if we shorten our front rod end here, this will also have the effect of moving our lower ball joint forward, increasing our caster.
05:52 So depending on what combination of track width and caster we actually want, we can adjust or manipulate the length of these two rod ends together.
06:01 The other thing to consider before making any adjustments is to ensure that we have sufficient engaged thread in each of our rod ends and you'll remember from the body of the course, we want to have at least 1.5 times the outside diameter of our thread engaged in the fabricated arm to make sure that it's going to be absolutely safe.
06:21 So let's go ahead, we'll remove one of these rod ends and just make sure that's what we've got.
06:29 With our rod end removed from the arm, we can measure the outside diameter of our thread and we can see that we end up with 15.8 millimetres.
06:36 Now while I am working in millimetres there, this is actually an imperial rod end so this is a 5/8th of an inch outside diameter.
06:44 Doesn't really matter though, the maths still works the same and if we take our 15.8 millimetres, multiply this by 1.5, we're looking for approximately 24 millimetres minimum of engaged thread.
06:56 So what we can now do is measure the amount of thread from out lock nut and we can see that in fact in this instance we've only got 21 millimetres available.
07:05 So what we would want to do is just move our jam nut further down the rod end, making sure that we've got at least 24 millimetres.
07:14 And this will give us a good guide here, just to ensure that when we have got the rod end installed, up to that jam nut we're going to know that we've got at least that 24 millimetres, a safe amount of thread, we can now reinstall this on the arm.
07:31 With our rod ends checked for engagement, we know that we're now safe so we can go ahead and transfer those measurements across from our factory control arm to this aftermarket arm, let's do that now.
07:50 So at this point we've made adjustments to our lower control arm and we have actually had to make a small compromise here, particularly in our track width or our distance between our rear bush and our lower ball joint.
08:02 And this is just to maintain that safe engagement with our rod end.
08:06 Of course that does become much more critical than geting our alignment perfect.
08:10 Again this is only getting us in the ballpark for our alignment.
08:13 So we're going to be able to make futher adjustments once we have these on the car.
08:17 Now that we've got our first lower control arm adjusted, we've got the task of repeating that process on our other control arm and here what we're trying to do is make sure that our adjustments are as accurate or even from one side of the car to the other.
08:31 Now if we don't do this, we risk problems with inaccurate track width from one side to the other or inaccurate wheel base and caster from one side of the car to the other.
08:41 And again, while we may need to make adjustments to these arms, once we've actually got them fitted to the car, we want to at least have a consistent starting point so they are both the same.
08:49 Now at this point you may be thinking, well if these arms are built in a jig then we could expect the arms to be exactly the same or mirror images of each other from one side to the other.
09:01 Particularly if you are dealing with billet suspension arms that have been CNC machined out of a piece of aluminium billet then yes you should likely be able to expect that which makes our adjustments much easier.
09:13 With fabricated arms, there is a lot more room for error creeping in because the jigs will be different from one side of the car to the other.
09:20 So our policy is always to trust but verify.
09:24 So what we want to do here is start by making sure that the dimensions of both arms are exactly the same.
09:30 In order to confirm the accuracy of the arms, we're just going to make three measurements here, essentially not too much different to what we've already done.
09:37 We're basically going to triangulate the suspension components and take those measurements, confirm them on the other arm.
09:44 This can be a little bit tricky, particularly due to the three dimensional design of some of the suspension arms.
09:50 And for example here in our outer cup where our lower ball joint spherical bearing is located, what we're looking for is a lip or a feature on this bush that we can use to make our measurement from.
10:04 So let's go ahead and take those measurements now.
10:11 We've taken our measurements on our first arm, we're now going to compare those to the measurements on the second arm and hopefully everything should be exactly the same.
10:23 So we've confirmed that these arms actually do measure up exactly the same, essentially they are mirror images of each other.
10:29 That's exactly what we would hope to achieve but again we always want to verify that that is the case.
10:36 With that cleared up, it makes our next adjustments much easier.
10:38 Rather than trying to transfer those measurements from our factory lower control arm onto our aftermarket arm like you've just seen me do, instead what we can do now is measure the protrusion of each of our rod ends on the arm that we've just set up and make sure that the protrusion of the rod ends on our second arm is exactly the same.
10:56 When it comes to measuring the protrusion of our rod ends, this can be a little bit tricky if you are trying to measure to the centre of the rod end.
11:02 This builds in a level of inaccuracy so instead what I like to do is choose a particular feature on the outside housing of the rod end, measure between there and the point where the thread locates into the fabricated arm itself and we can measure this using a set of digital verniers.
11:19 Let's go ahead and do that now.
11:21 To illustrate what I'm talking about here, if we inspect this particular rod end, we can see there's a little machined lip here and I'm going to use this as my reference point.
11:29 We're going to be using our digital verniers to measure between this point here and the end of our suspension arm.
11:35 Let's see how that works out.
11:40 So we can see that that particular measurement there is 15.02 millimetres.
11:44 15 millimetres is close enough for our purposes.
11:48 Let's now transfer that measurement across onto our other component.
11:55 So we can see that both of our measurements there match and we're simply going to repeat that process for our other rod ends and following this process means that we can be really confident that both lower control arms are exactly the same, meaning that our wheel base and our track are going to be consistent from one side of the car to the other.
12:13 Now while we've just look at setting up a pair of lower control arms, the techniques that we've just looked at can of course be applied to any aftermarket suspension arm.
12:22 For example here we've got a set of toe control arms.
12:25 And these actually become a little bit easier to check and adjust.
12:29 What we want to do here is first of all start by measuring the fabricated component of both arms, making sure that they are consistent.
12:37 Now these will have been made on the same jig so we can be relatively certain that they will be, but again, trust but verify.
12:44 So let's take some measurements there.
12:49 So as we can see, both of the fabricated components here of our toe control arms measure exactly the same, making our job very easy.
12:56 We can make our adjustments to these arms simply by measuring the protrusion of the rod ends and ensuring that they are the same for both sides.
13:04 So the techniques that we've look at here can be applied to any of our other suspension components.